The present invention relates to a method for producing a rubber glove comprising natural rubber or synthetic rubber. More particularly, the invention relates to a rubber glove for home use, examination, operation and work, which is hygienic and can be easily worn and removed, and a method capable of producing the rubber glove stably and continuously.
Generally, a rubber glove produced from natural rubber or synthetic rubber is tacky on its inner and outer surfaces. Thus, the rubber gloves adhere to each other during storage, and are difficult to wear and remove when in use. Various contrivances have been applied to this kind of rubber glove in order to eliminate tackiness or facilitate wearing and removal. To prevent tackiness of the outer surface of the glove, for example, various methods, as shown in (1) to (3) below, are carried out:
(1) A fine powder of calcium carbonate is added beforehand to a coagulating liquid composition containing a rubber latex coagulant to adhere the fine powder onto the surface of a rubber glove.
(2) The surface of rubber is chlorinated.
(3) A silicone oil or a fluorine-based surface active agent is applied to the surface of the rubber glove.
Of the above methods, the methods (1) and (2) are useful in economy, wearability/removability, and stable production, and they are the mainstream for production of rubber gloves. However, these methods pose the following problems: With the method (1), fine calcium carbonate powder is used. Thus, the fine powder easily falls off the surface of the glove, and the intended anti-tack effect cannot persist. Nor is this method preferred from hygienic and environmental aspects. For example, protein remaining in the rubber scatters by the medium of the calcium carbonate powder, causing allergy, etc. According to the method (2), the resulting rubber glove is demolded, and then chlorinated. Thus, the number of the treatment steps increases, and it is difficult to control the treatment process for chlorination (e.g., degree of chlorination, degree of washing with water for neutralization, uniform treatment). As a result, the rubber itself may decrease in strength, or change in color. Furthermore, residual chlorine gives off an odor, and the chlorination process exerts influences on the environment. The method (3), on the other hand, requires the step of applying a silicone oil or a fluorine-based surface active agent, thus increasing the number of treatment steps and decreasing productivity.
The present invention has been accomplished to solve the above-described problems with the earlier technologies. It is an object of this invention to provide a method for producing a rubber glove, which is excellent in anti-blocking properties and also in grip under dry or wet conditions, inexpensively by a simple method. Another object of the invention is to provide a method for producing a rubber glove, which is free from a decrease in the strength of the rubber itself, free from discoloration, and very comfortable to use, by a simple process, without causing any problems to hygiene and environment during production.
A first aspect of the present invention is a method for producing a rubber glove, comprising the steps of:
immersing a glove mold in a coagulating synthetic rubber latex containing one substance selected from the group consisting of thermally expansible microcapsules and a blowing agent, a rubber coagulant, and synthetic rubber in latex form stable to the rubber coagulant to form a coagulant-containing synthetic rubber film on a surface of the glove mold;
then immersing the glove mold in rubber-incorporating latex to form a gelled rubber layer on the coagulant-containing synthetic rubber film;
then heating the resulting two-layer rubber laminate to vulcanize and foam it; and
demolding the vulcanized rubber laminate from the glove mold as it is turned inside out.
The present invention also relates to a two-layer rubber glove having a synthetic rubber film layer formed on an outer surface of a glove body rubber layer, the rubber glove being prepared by the method for production described above.
A second aspect of the present invention is a method for producing a rubber glove, comprising the steps of:
immersing a glove mold in a coagulating synthetic rubber latex containing one substance selected from the group consisting of thermally expansible microcapsules and a blowing agent, a rubber coagulant, and synthetic rubber in latex form stable to the rubber coagulant to form a coagulant-containing synthetic rubber film on a surface of the glove mold;
then immersing the glove mold in rubber-incorporating latex to form a gelled rubber layer on the coagulant-containing synthetic rubber film;
then immersing the glove mold, which has a two-layer rubber laminate formed thereon, in an aqueous dispersion containing synthetic rubber in latex form and organic fine particles to form an organic fine particle-containing synthetic rubber latex layer on the gelled rubber layer;
then heating the resulting three-layer rubber laminate to vulcanize and foam it; and
demolding the vulcanized rubber laminate from the glove mold as it is turned inside out.
The present invention also relates to a three-layer rubber glove having a synthetic rubber film layer formed on an outer surface of a glove body rubber layer, and a lubricating resin layer formed on an inner surface of the glove body rubber layer, the rubber glove being prepared by the method for production described above.
The content of the thermally expansible microcapsules or blowing agent in the coagulating synthetic rubber latex is preferably 5 to 150 parts by weight for 100 parts by weight of the solids of the synthetic rubber in latex form. A rubber vulcanizing agent is preferably contained in the coagulating synthetic rubber latex. The content of the rubber vulcanizing agent in the coagulating synthetic rubber latex is preferably 0.5 to 10 parts by weight for 100 parts by weight of the solids of the synthetic rubber in latex form.
The rubber vulcanizing agent is preferably at least one substance selected from sulfur, zinc oxide, an inorganic salt of dithiocarbamic acid, and thiuram polysulfide.
In the coagulating synthetic rubber latex, at least one substance selected from an emulsion type silicone oil, a fine powder of synthetic resin, and a fine powder of an inorganic oxide is contained in an amount of 0.1 to 50 parts by weight for 100 parts by weight of the solids of the synthetic rubber in latex form.
A third aspect of the present invention is a method for producing a rubber glove, comprising the steps of:
immersing a glove mold in a coagulating liquid composition containing a rubber vulcanizing agent and a rubber coagulant to adhere the rubber vulcanizing agent and the rubber coagulant onto a surface of the glove mold;
then immersing the glove mold in rubber-incorporating latex to form a gelled rubber layer;
then heating the resulting two-layer rubber laminate to vulcanize it; and
demolding the vulcanized rubber laminate from the glove mold as it is turned inside out.
The present invention also relates to a highly vulcanized three-layer rubber glove.
A fourth aspect of the present invention is a method for producing a rubber glove, comprising the steps of:
immersing a glove mold in a coagulating liquid composition containing a rubber vulcanizing agent and a rubber coagulant to adhere the rubber vulcanizing agent and the rubber coagulant onto a surface of the glove mold;
then immersing the glove mold in rubber-incorporating latex to form a gelled rubber layer;
then immersing the glove mold, which has the gelled rubber layer formed thereon, in an aqueous dispersion containing synthetic rubber latex and organic fine particles to form an organic fine particle-containing synthetic rubber latex layer on the gelled rubber layer;
then heating the gelled rubber layer and the organic fine particle-containing synthetic rubber latex layer to vulcanize them, thereby forming a laminate comprising the vulcanized rubber layer and a lubricating resin layer; and
then turning the vulcanized laminate inside out, and demolding it from the glove mold.
The present invention also relates to a rubber glove having a lubricating resin layer on an inner surface of a rubber layer, the rubber glove being prepared by the method for production described above.
The content of the rubber vulcanizing agent in the coagulating liquid composition is preferably 0.5 to 10% by weight. The rubber vulcanizing agent is preferably at least one substance selected from the group consisting of sulfur, zinc oxide, a salt of dithiocarbamic acid, and thiuram polysulfide.
The coagulating liquid composition preferably contains 0.1 to 20% by weight of at least one substance selected from the group consisting of an emulsion type silicone resin, a powder of synthetic resin, and a fine powder of an inorganic oxide.
The above-described method for producing a rubber glove may further comprise depositing starch or talc fine powder on a surface of the gelled rubber layer.
In the method for production according to the first or second aspect of the invention, the content of the thermally expansible microcapsules or blowing agent in the coagulating synthetic rubber latex is preferably 5 to 150 parts by weight for 100 parts by weight of the solids of the synthetic rubber in latex form.
Preferably, a rubber vulcanizing agent is contained in the coagulating synthetic rubber latex. Further preferably, at least one substance selected from an emulsion type silicone oil, a fine powder of synthetic resin, and a fine powder of an inorganic oxide may be contained.
According to the method for production of the present invention, a glove mold is immersed in a coagulating synthetic rubber latex containing synthetic rubber latex, one substance selected from the group consisting of thermally expansible microcapsules and a blowing agent, and a rubber coagulant to adhere a synthetic rubber film, which contains the thermally expansible microcapsules or blowing agent in a high concentration, onto the surface of the glove mold. Thus, when a gelled rubber layer formed thereon is heated and vulcanized, the thermally expansible microcapsules or blowing agent is foamed to form a rough surface having asperities on the surface of the rubber layer, namely, the outer surface of the glove, thereby resulting in a loss of tackiness on the surface of the glove. According to the present invention, therefore, a rubber glove with high anti-blocking properties and high grip can be prepared by a series of steps ending with demolding which constitute a so-called in-line process.